1. Technical Field
The present invention relates to a semiconductor device, and, more particularly, to a semiconductor device including an electric fuse.
2. Related Art
Conventionally, there has been known a technology according to which a fuse is installed in a semiconductor device, the fuse is cut to adjust a resistance value used in the semiconductor device, to remove a defective element for replacement by a normal element, and the like.
In order to cut or disconnect a fuse, there has been used a method, by which a fuse is cut by irradiating a part of the fuse with beams of laser light, or a method of cutting a fuse by use of an electric current.
Japanese Laid-open patent publication No. 2005-39220 has disclosed a fuse which can be cut by a smaller current. In Japanese Laid-open patent publication No. 2005-39220, a conductive material forming the fuse is shaped to be folded up a plurality of times. FIG. 21 is a plan view showing the fuse disclosed in Japanese Laid-open patent publication No. 2005-39220. Here, a fuse 1100 is folded up twice.
The fuse 1100 includes a current flowing-in terminal 1101, and a current flowing-out terminal 1102, and further has a first one-way straight-line portion 1103, an another-way straight-line portion 1104, and a second one-way straight-line portion 1113 between the current flowing-in terminal 1101 and the current flowing-out terminal 1102. The fuse 1100 further includes a first right-angle connecting portion 1106 connecting the first one-way straight-line portion 1103 and the another-way straight-line portion 1104, and a second right-angle connecting portion 1107 connecting the second one-way straight-line portion 1113 and the another-way straight-line portion 1104.
In the fuse 1100 with the above-described configuration, when a predetermined current is applied to the current flowing-out terminal 1102 from the current flowing-in terminal 1101, cutting the another-way straight-line portion 1104 between the diagonally shaded portion 1109 is accelerated by adding heat generated in a diagonally shaded portion 1108 in the outer portion of the fuse 1100 to heat generated in the diagonally shaded portion 1109 in the inner portion of the fuse 1100. Thereby, the fuse 1100 is easily cut.
Moreover, Japanese Laid-open patent publication No. 2005-57186 has disclosed a configuration in which, when a current is applied to a fuse, heat generated in a portion of the fuse, which is to be cut, is trapped or accumulated in the neighborhood of the portion in the fuse, which is to be cut, by enclosing the portion with a plate.
In Japanese Laid-open patent publication No. 2005-39220 and Japanese Laid-open patent publication No. 2005-57186, a fuse is heated to melt a material forming the conductive material in the fuse, or a fuse is cut, using a movement phenomenon caused by electro-migration, when a current is applied to the fuse.
Incidentally, when a fuse is formed with a material which moves by the electro-migration, it may be considered that material movement by the electro-migration causes reconnection at a cut part when heat-treating of a semiconductor device is executed after the fuse is cut. If such reconnection is caused, a correct result will not be obtained at detecting whether the electric fuse is cut even if the electric fuse to be cut has been cut.
Though it is thought that a possibility that the above-described reconnection is caused is not so high, and there is no problem at ordinary use, it is required to improve a holding characteristic by which a state, in which an electric fuse is cut, is held, when demand for the higher reliability of a semiconductor device is much increased or when a semiconductor device is used under severe conditions, or the like.